What does this tool do?
The Factorial Calculator computes the factorial of an integer n (n!), which is the product of all positive integers from 1 up to n. Because it uses BigInt, it returns exact results even for very large numbers, making it ideal for students, anyone working with combinations and permutations, and the mathematically curious.
How to use it
- Enter your values into the fields.
- The result is calculated instantly.
- Read or copy the result.
What a factorial is and how it works
n! means n × (n−1) × … × 2 × 1; for example 5! = 120 and 10! = 3,628,800. By definition 0! = 1. This tool accepts values from 0 to 2000 and computes the result with JavaScript's BigInt type, so nothing is rounded. If you enter a negative number you get a warning, since factorial is undefined for negatives. The number of digits in the result is shown alongside it.
Where factorials are used
Factorials are fundamental in probability and combinatorics: the number of ways to order n items (permutations) is n!, and combinations are n! / (k!(n−k)!). They appear in binomial coefficients, Taylor series, and countless math problems. For instance, the number of ways to shuffle a 52-card deck is 52!, a staggering 68-digit number, which the tool displays exactly and instantly.
Frequently asked questions
Why is 2000 the maximum input?
2000! is already a huge number with 5,735 digits. The upper limit is capped at 2000 to keep your browser responsive; larger values trigger a 'Number too large' message.
Why does 0! equal 1?
The value of an empty product is 1 by definition, which keeps combination formulas consistent. The tool returns 0! = 1 accordingly.
Why is the result a very long integer instead of a decimal?
Factorials grow rapidly, and this tool uses BigInt to show the exact whole number with every digit, without rounding or scientific notation.
Is Factorial Calculator free?
Yes. Factorial Calculator and all 300+ tools on MagmaNex are completely free with no signup or account required.
Is my data safe?
Yes. Everything runs locally in your browser. The data you enter is never sent to a server, stored, or shared.
Does it work on mobile?
Yes. Factorial Calculator works on phones, tablets and desktops — no app download needed.
🔒 Privacy: everything runs in your browser, your data is never sent to a server.